From 2d8f5a52f76f9bff318e061f73dd931c012cf940 Mon Sep 17 00:00:00 2001
From: Sorunome <mail@sorunome.de>
Date: Wed, 3 Jun 2020 20:46:08 +0200
Subject: [PATCH] better handle frames
---
.../thumbnail_resource_handler.go | 37 ++++++-------------
1 file changed, 12 insertions(+), 25 deletions(-)
diff --git a/controllers/thumbnail_controller/thumbnail_resource_handler.go b/controllers/thumbnail_controller/thumbnail_resource_handler.go
index 521afb65..11ed6f88 100644
--- a/controllers/thumbnail_controller/thumbnail_resource_handler.go
+++ b/controllers/thumbnail_controller/thumbnail_resource_handler.go
@@ -5,7 +5,6 @@ import (
"errors"
"fmt"
"image"
- "image/color"
"image/draw"
"image/gif"
"io"
@@ -240,23 +239,29 @@ func GenerateThumbnail(media *types.Media, width int, height int, method string,
// Prepare a blank frame to use as swap space
frameImg := image.NewRGBA(image.Rectangle{image.Point{0, 0}, image.Point{g.Config.Width, g.Config.Height}})
- // make sure the image is transparent at the start
- draw.Draw(frameImg, frameImg.Bounds(), image.Transparent, image.ZP, draw.Src)
for i := range g.Image {
img := g.Image[i]
var disposal byte
if g.Disposal == nil {
- // go 1.14
disposal = 0
} else {
disposal = g.Disposal[i]
}
- var previousImg draw.Image
+ // if disposal type is 1 (preserve previous frame) we can get artifacts from re-scaling
+ // as such, we re-render those frames to disposal type 0 (start with a transparent frame)
+ // see https://www.w3.org/Graphics/GIF/spec-gif89a.txt
+ if disposal == 1 {
+ g.Disposal[i] = 0
+ } else {
+ draw.Draw(frameImg, frameImg.Bounds(), image.Transparent, image.ZP, draw.Src)
+ }
+
+ var previousFrameImg draw.Image
if disposal == 3 {
- previousImg = image.NewRGBA(g.Image[0].Bounds())
- draw.Draw(previousImg, frameImg.Bounds(), frameImg, image.ZP, draw.Over)
+ previousFrameImg = image.NewRGBA(frameImg.Bounds())
+ draw.Draw(previousFrameImg, frameImg.Bounds(), frameImg, image.ZP, draw.Over)
}
// Copy the frame to a new image and use that
@@ -274,24 +279,6 @@ func GenerateThumbnail(media *types.Media, width int, height int, method string,
targetImg := image.NewPaletted(frameThumb.Bounds(), img.Palette)
draw.FloydSteinberg.Draw(targetImg, frameThumb.Bounds(), frameThumb, image.ZP)
g.Image[i] = targetImg
-
- // determine how to dispose the frame
- // see https://www.w3.org/Graphics/GIF/spec-gif89a.txt
- if disposal == 0 {
- // Clear the transparency of the previous frame
- draw.Draw(frameImg, frameImg.Bounds(), image.Transparent, image.ZP, draw.Src)
- } else if disposal == 1 {
- // do nothing
- } else if disposal == 2 && g.Config.ColorModel != nil {
- // restore background color
- background := g.Config.ColorModel.(color.Palette)[g.BackgroundIndex]
- if background != nil {
- draw.Draw(frameImg, frameImg.Bounds(), image.NewUniform(background), image.ZP, draw.Src)
- }
- } else if disposal == 3 && previousImg != nil {
- // restore previous frame
- draw.Draw(frameImg, frameImg.Bounds(), previousImg, image.ZP, draw.Over)
- }
}
// Set the image size to the first frame's size
--
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